Related Experiment Video
Updated: May 23, 2026
Investigations on the Ga(III) Complex of EOB-DTPA and Its 68Ga Radiolabeled Analogue
Published on: August 17, 2016
Bone-seeking TRAP conjugates: surprising observations and their implications on the development of gallium-68-labeled
Johannes Notni1, Jan Plutnar, Hans-Jürgen Wester
1Pharmaceutical Radiochemistry, Technische Universität München, Walther-Meissner-Str, 3, Garching 85748, Germany. johannes.notni@tum.de.
Background:
Bisphosphonates possess strong affinity to bone. 99mTc bisphosphonate complexes are widely used for bone scintigraphy. For positron emission tomography (PET) bone imaging, Ga-68-based PET tracers based on bisphosphonates are highly desirable.
Findings:
Two trimeric bisphosphonate conjugates of the triazacyclononane-phosphinate (TRAP) chelator were synthesized, labeled with Ga-68, and used for microPET imaging of bone in male Lewis rats. Both Ga-68 tracers show bone uptake and, thus, are suitable for PET bone imaging. Surprisingly, Ga-71 nuclear magnetic resonance data prove that Ga(III) is not located in the chelating cavity of TRAP and must therefore be bound by the conjugated bisphosphonate units.
Conclusion:
The intrinsic Ga-68 chelating properties of TRAP are not needed for Ga-68 PET bone imaging with TRAP-bisphosphonate conjugates. Here, TRAP serves only as a trimeric scaffold. For preparation of Ga-68-based bone seekers for PET, it appears sufficient to equip branched scaffolds with multiple bisphosphonate units, which serve both Ga-68-binding and bone-targeting purposes.
![Automated Preparation of [68Ga]Ga-3BP-3940 on a Synthesis Module for PET Imaging of the Tumor Microenvironment](/_next/image?url=https%3A%2F%2Fcloudfront.jove.com%2FCDNSource%2Fteasers%2F68356.jpg&w=3840&q=50)